The present invention relates generally to prosthetic devices, and more particularly, to a coupling component for use in coupling a prosthetic limb socket assembly to a prosthetic limb upright assembly, that is specifically adapted to compensate for flexion contracture of a patient's residual limb.
FIG. 1 shows an example of a prior art socket assembly for a prosthetic limb. The prior art socket assembly includes a rigid molded plastic socket 10 sized and shaped to receive a patient's residual limb therein, a locking device 12 (such as a “shuttle lock”) positioned at the distal end of the rigid socket 10, interconnection components 14 for maintaining the lock 12 within the socket 10 and for mounting other components of the prosthetic limb to the distal end of the socket, and a silicone sleeve 16 adapted to be snugly fitted (rolled onto) the patient's residual limb. The silicone sleeve 16 includes a plate 18 molded therein having an internally threaded boss 20 extending therefrom. A plunger pin 22 includes an externally threaded proximal end 24 adapted to be attached to the internally threaded boss 20 of the attachment plate 18 and includes a ratcheted distal end 26 that is adapted to be received within the center hole 28 of the lock 12 and to be locked within the center hole by a spring-loaded pawl (not shown).
To don the prosthetic limb, the patient will roll on or slip on the silicone sleeve 16 so that the plunger pin 22 extends distally from the patient's residual limb and will then insert the residual limb into the plastic socket 10 such that the plunger pin 22 engages with the lock 12. To release the plunger pin 22 from the lock 12, a button 30 on the lock is activated to remove the pawl from within the center hole 28, thereby releasing the ratcheted distal end 26 of the plunger pin from within the center hole 28. Referring to FIG. 2, the interconnection components (not shown in FIG. 2) will be utilized to couple the distal end of the socket 10 to the proximal end of the upright assembly 32 of the prosthetic limb. For the purposes of the present application, the upright assembly is all components, or combination of components, coupled to the distal end of the prosthetic limb socket. The upright assembly, in this example, includes a prosthetic knee joint 34, coupled to the proximal end of a leg shaft 36, which is, in turn, coupled to a proximal end of a prosthetic foot component 38. Another example of an upright assembly may merely comprise a prosthetic foot assembly.
Acceptable alignment for a transfemoral patient's prosthesis is to align, from the lateral side, the Trocanter (T), Knee axis (K) and Ankle axis (A) in a vertical line, illustrated by numeral 40. There are many different types and designs of modular attachment components for use in coupling the distal surface of the prosthetic limb socket 10 to the proximal end of the knee chassis 34. Some of these components offer angular, rotational and horizontal translational adjustments independently that allow the prosthetist to align the prosthesis and maintain a proper alignment or TKA line. If the TKA line is not maintained, normal gait may be unachievable. TKA alignment for a prosthetic limb is even more troublesome in cases where the patient's residual limb experiences a substantial amount of flexion contracture, which can be defined as the angle between the body weight line perpendicular to the ground and the bisector line of the lateral aspect of the flexed residual limb.
If a prosthetist were to use a sliding/rotating pyramid receiver (commercially available from Prosthetic Design, Inc., p/n PR-SL-R, described in U.S. patent application Ser. No. 09/613,977, entitled COUPLING-SOCKET ADAPTOR ASSEMBLY FOR A PROSTHETIC LIMB) and a fixed pyramid connector for coupling the proximal end of the knee chassis 34 to the distal end of the prosthetic limb socket 10, the prosthetist would be able to slide the sliding/rotating pyramid receiver up to one-half inch (½″) off-center in either a medial/lateral direction or an anterior/posterior direction. In addition, the prosthetist would have angular adjustments available up to ten degrees (10°) and unlimited rotational adjustments. However, if a transfemoral amputee has a flexion contracture of ten degrees (10°) and a residual limb length of twelve inches (12″) trocanter to the distal surface of the socket, the attachment components need to accommodate the ten degree angle and an offset of 2.08 inches (2.08″). Since there are no commercially available attachment components that feature a drastic offset an angle to maintain the TKA line, the prosthetist and/or technician would need to fabricate the prosthesis in a way that incorporates the offset angle for the patient that has flexion contracture. A problem with this custom fabrication, is that the process for fabricating the prosthesis to incorporate an offset of 2.08 inches and ten degrees flexion contracture, for example, is very labor-intensive, time consuming and challenging.